Method for forming patterned photoresist

ABSTRACT

A method of forming a patterned photoresist layer includes the following operations: (i) forming a patterned photoresist on a substrate; (ii) forming a molding layer covering the patterned photoresist; (iii) reflowing the patterned photoresist in the molding layer; and (iv) removing the molding layer from the reflowed patterned photoresist. In some embodiments, the molding layer has a glass transition temperature that is greater than or equal to the glass transition temperature of the patterned photoresist. In yet some embodiments, the molding layer has a glass transition temperature that is 3° C.-30° C. less than the glass transition temperature of the patterned photoresist.

This application claims priority to U.S. Provisional Application Ser.No. 62/894,367, filed Aug. 30, 2019, which is herein incorporated byreference in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological progress in IC manufacture has produced severalgenerations of ICs, and each generation fabricates smaller and morecomplex circuits than the previous generation. Several advancedtechniques have been developed to implement technique nodes with smallerfeature sizes. For instance, extreme ultraviolet (EUV) technologies havebeen applied in the pattern formation of the photoresist. Although theEUV technologies and the photoresist material have contributed to theshrinkage of the critical dimension of the circuit, these technologieshave not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a flow chart illustrating a method according to variousembodiments of the present disclosure.

FIGS. 2-9 collectively illustrate more detailed manufacturing methodsassociated with the method of FIG. 1 in accordance with variousembodiments of the present disclosure.

FIG. 10 is a flow chart illustrating a method according to yet variousembodiments of the present disclosure.

FIGS. 11-15 schematically depict the cross-sectional views in variousprocess stages of the method of FIG. 10

FIG. 16 is a follow chart illustrating a method according to yet someembodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

The semiconductor industry has continually improved the speed and powerof integrated circuits (ICs) by reducing the size of components withinthe ICs. Several advanced techniques have been developed to implementtechnique nodes with smaller feature sizes. One of the key points is thephotoresist and the extreme ultraviolet (EUV) technologies. Although theEUV exposing technologies have manufactured photoresists with linewidthof several nanometers, the throughput is the major issue in terms of themanufacturing cost. The photoresist material suitable for the EUVexposure typically needs a high dose of exposure in terms of an accuracypattern. The high dose of exposure requires high power of the lightsource for the purpose of increasing manufacturing throughput. The powerof the light source in EUV equipment, however, has merely increasedmarginally in recent years. Since the power of light source is limited,the exposing duration of time must to be increased, which suffers themanufacturing throughput and is unfavorable to the manufacturing cost.

Another one of the solutions turns to the composition of the photoresistin pursuit of high throughput. For example, the photo-acid generator(PAG) could be possibly improved to become more efficient; or theloading to the photo-acid generator could be increased, accompanyingwith changes in other components; or the acid-liable groups (ALG) of thephotoresist could be improved to become more sensitive. However, all ofthe aforementioned approaches require a long-term development and strictverifications in the manufacturing line. According to one of the aspectof the present disclosure, the manufacturing throughput is increased bypost-treatments, which is cost-effective and compatible with the currentprocess of forming photoresist.

The following disclosure provides many different embodiments or examplesfor implementing different features of the present disclosure. Specificexamples of components and permutations are described below to simplifythe disclosure of the present disclosure. Of course, the examples aremerely examples and are not intended to be limiting. For example, in thefollowing description, the disclosure of the first feature being formedon or above the second feature includes an embodiment in which the firstfeature is in direct contact with the second feature, and may alsoinclude an embodiment in which the first feature is not in directcontact with the second feature.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the embodiments. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Still further, when a number or a range of numbers is described with“about,” “approximate,” and the like, the term is intended to encompassnumbers that are within a reasonable range including the numberdescribed, such as within +/−10% of the number described or other valuesas understood by person skilled in the art. For example, the term “about5 nm” encompasses the dimension range from 4.5 nm to 5.5 nm.

FIG. 1 is a flow chart illustrating a method 10 according to variousembodiments of the present disclosure. The method 10 may be a method offorming a patterned masking layer such as for example a patternedphotoresist layer. FIGS. 2-9 collectively illustrate more detailedmanufacturing methods associated with the method 10 of FIG. 1 inaccordance with various embodiments of the present disclosure. It willbe appreciated that although these methods each illustrate a number ofoperations, acts and/or features, not all of these operations, actsand/or features are necessarily required, and other un-illustratedoperations, acts and/or features may also be present. Also, the orderingof the operations and/or acts in some embodiments can vary from what isillustrated in these figures. In addition, the illustrated acts can befurther divided into sub-acts in some implementations, while in otherimplementations some of the illustrated acts can be carried outconcurrently with one another.

Referring to FIG. 1, the method 10 includes an operation S11 of forminga patterned photoresist on a substrate. In the present disclosure, theterms “patterned photoresist” and “patterned photoresist layer” may bealternately used. FIGS. 2-3 are cross-sectional views schematicallydepicting detailed steps to implement the operation S11 according tosome embodiments of the present disclosure. As shown in FIG. 2, aphotoresist layer 106 is formed on a substrate 100 in a blanket manner.In specifics, a photoresist solution may be applied (e.g., coating) onthe substrate 100, and followed by a drying process to form thephotoresist layer 106 which is blanketly formed on the substrate 100.

In various embodiments, the substrate 100 may include a semiconductorsubstrate. The semiconductor substrate, for example, may includesilicon. In some embodiments, the semiconductor substrate may includeother elementary semiconductor such as for example germanium. In yetsome embodiments, the semiconductor substrate may include an alloysemiconductor such as for example silicon germanium, silicon germaniumcarbide, gallium indium phosphide and the like. In yet some embodiments,the semiconductor substrate may include compound semiconductor such asfor example gallium arsenic, silicon carbide, indium phosphide, indiumarsenide and the like. In yet some embodiments, the semiconductorsubstrate may include a semiconductor-on-insulator (SO1) structure. Inyet some embodiments, the semiconductor substrate may include anepitaxial layer overlying a bulk semiconductor material.

In some embodiments, the substrate 100 may further include a bottomanti-reflective layer (not shown) over the semiconductor substrate. Thebottom anti-reflective layer may work to prevent the uncontrolled andundesired reflection of energy (e.g., light) such as light back into theoverlying photoresist during an exposure of the photoresist, therebypreventing the reflecting light from causing reactions in an undesiredregion of the photoresist. Additionally, the bottom anti-reflectivelayer may be used to provide a planar surface over the semiconductorsubstrate, helping to reduce the negative effects of the energyimpinging at an angle.

In some embodiments, the photoresist layer 106 may be a chemicalamplified photoresist. The chemical amplified photoresist, for example,may include polymeric substance with additives including photo acidgenerator (PAG), quencher, etc. The polymeric substance includes polymerchains having hydrophobic acid-labile groups (ALGs), which is capable ofbeing transformed into hydrophilic groups by reaction with acids (e.g.,protons (H⁺)).

Thereafter, as shown in FIG. 3, an exposure process and a developingprocess are carried out to form a patterned photoresist layer 110.According to some embodiments of the present disclosure, the exposureprocess may include a step of exposing the photoresist layer 106 througha reticle (i.e., photomask) 104 by using an extreme ultraviolet (EUV)beam 102 with a wavelength of about 13.5 nm or less. The reticle 104 hasa plurality of transparent regions through which the EUV beam 102transmits to the photoresist layer 106. In some examples, as thephotoresist layer 106 is illuminated by the EUV beam 102, the PAGs inthe photoresist layer 106 produce acids, which release protons (H⁺). Thereleased protons react with the hydrophobic ALGs of the photoresistlayer 106 so as to convert the hydrophobic ALGs into hydrophilic groups.In some embodiments, the EUV beam 102 is supplied with a dose of lessthan a saturation value in terms of the critical dimension uniformity(CDU) in order to increase the manufacturing throughput. In examples,the dose of the EUV beam 102 may be equal to or less than 40 mJ/cm², forexample 30 mJ/cm², 20 mJ/cm², 10 mJ/cm² or less. Reference iscontinuously made to FIG. 4, which is a top view schematically showingthe patterned photoresist layer 110. After the developing process, theformed patterned photoresist layer 110 has a rough edge (namely, “lineedge roughness” (LER)). In specifics, the rough edge or sidewall of thepatterned photoresist layer 110 has a number of micro protrusions andmicro cavities (or recesses). Without being bonded to any theory, it isbelieved that a low EUV dose is insufficient to adequately convert thehydrophobic ALGs at the edge of the exposed region into hydrophilicgroups. The rough edge of the patterned photoresist layer 110 isundesirable because this rough edge considerably decreases the accuracyof the fabricated circuit and lowers the manufacturing yield. However,the low EUV dose may significantly increase the manufacturingthroughput. According to one of the aspects of the present disclosure,the benefits of the usage of the low EUV dose is gained, but thedrawbacks of the LER issue is improved or remedied by the followingprocesses.

In some embodiments, the patterned photoresist layer 110 includes aplurality of apertures 112 exposing the substrate 100. Although FIGS. 3and 4 depict only an aperture 112 and a simple pattern of the patternedphotoresist layer 110, it is noted the pattern of the patternedphotoresist layer 110 may be complex and include a number of regular orirregular apertures 112.

Referring back to FIG. 1, the method 10 proceeds to operation S12 byforming a molding layer covering the patterned photoresist. FIG. 5 is across-sectional view schematically showing the structure after theoperation S12 is carried out, according to some embodiments of thepresent disclosure. As shown in FIG. 5, a molding layer 120 is formedcovering the patterned photoresist layer 110. In examples, a solutioncontaining a molding material may be applied (e.g., coating) to from alayer of molding solution which covers the patterned photoresist layer110 on the substrate 100. Thereafter, a drying process may be carriedout to remove the solvent in the molding solution so as to form themolding layer 120.

In some embodiments, the molding layer 120 does not completely fill themicro cavities or recesses on the edge of the patterned photoresistlayer 110. Accordingly, there exists tiny space 114 between the moldinglayer 120 and the rough sidewall of the patterned photoresist layer 110,as shown in FIG. 5. In specifics, the molding solution may have arelatively higher surface tension, and therefore the applied moldingsolution does not completely fills the micro cavities or recesses on therough sidewall of the patterned photoresist layer 110. As a result,after the molding solution is dried, the tiny space is still present inbetween the molding layer 120 and the sidewall of the patternedphotoresist layer 110.

However, in yet some embodiments, the molding layer 120 may fill up themicro cavities or recesses on the sidewall of the patterned photoresistlayer 110, which will be described in detail hereinafter in connectionwith FIGS. 8 and 9.

In some embodiments, the molding layer 120 is formed with a thicknessgreater than the thickness of the patterned photoresist layer 110.Accordingly, the apertures 112 of the patterned photoresist layer 110are filled up with the molding layer 120 in some examples of the presentdisclosure. In other words, the patterned photoresist layer 110 may beencapsulated in the molding layer 120.

In some embodiments, the molding layer 120 may be made with a polymerwhich has a repeating unit including at least one of a hydroxylfunctionality, a carboxylate functionality, a carboxylic acidfunctionality, an amine functionality, and an amide functionality. Inexamples, the polymer of the molding layer 120 may be poly(acrylicacid), poly(methacrylic acid), poly(acrylamide), poly(N-vinylacetamide), poly(vinyl alcohol), poly(4-vinylphenol),poly(4-styrenesulfonic acid),poly(2-acrylamido-2-methyl-1-propanesulfonic acid), or a combinationthereof. In specifics, the polymer may be represented by the followingFormulas (1)-(8):

in which n is an integral number ranged from 3-20,000. In yet someembodiments, the polymer has a molecular weight of 50-1,000,000,specifically 100-100,000, more specifically 500-50,000.

In some embodiments the polymer may be poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS). PEDOT:PSS includes the repeatingunits represented by the formulas of:

In some embodiments, the polymer of the molding layer 120 may be acopolymer, which includes at least two of the repeating units ofFormulas (1)-(8). For examples, the polymer of the molding layer 120 maybe poly(acrylic acid-co-acrylamide), poly(methacrylicacid-co-4-vinylphenol), or poly(4-styrenesulfonic acid-co-maleic acid),or a combination thereof. In specifics, the illustrative examples of thecopolymer may be represented by the following Formulas (9)-(11):

in which the symbol “

” represent any connecting group or naught, x is an integral numberranged from 3-20,000, and y is an integral number ranged from 3-20,000.In yet some examples, the copolymer has a molecular weight of50-1,000,000, specifically 100-100,000, more specifically 500-50,000.

In some embodiments, the polymer of the molding layer 120 may be ablending polymer which includes two or more polymers or copolymersdescribed hereinbefore, e.g., two or more selected from formulas(1)-(11).

In some embodiments, the molding layer 120 may further include aplasticizer. Illustrative examples of the plasticizer includesdi(2-ethylhexyl) phthalate (DEHP), diisononylcyclohexane-1,2-dicarboxylate (DINCH), succinate, maleate, and the like,and a combination thereof. In specifics, the illustrative examples ofthe plasticizer may be represented by the following Formulas (12)-(15):

in which R and R′ independently may be a hydrogen atom, an alkyl grouphaving 1 to 12 carbon atoms, an alkenyl group having 1 to 12 carbonatoms, an alkynyl group having 1 to 12 carbon atoms, an arly grouphaving 1 to 18 carbon atoms, a heterocyclic group having 1 to 18 carbonatoms. R and/or R′ may be substituted with at least one of the groupselected from a carboxylic group, a hydroxyl group, an aldehyde group,an amine group, an amido group, a sulfide group, a sulfoxide group, anda sulfone group.

In some embodiments, the molding layer 120 may further include a basematerial that is dispersed in the polymer. The base material may be anorganic base. For instance, the organic base may be primary amine, asecondary amine, or a tertiary amine. Illustrative examples of the basematerial includes ammonium hydroxide (NH4OH), (2-methylbutyl)amine,(3-methylpentyl)amine, 2,4,6-trimethylpyridin-3-amine,5-methylpyrimidin-2-amine and the like, and a combination thereof. Inyet some examples, the base material may be a polymer includingfunctional groups of —NH₂, such as poly(vinyl amine). The illustrativeexamples of the plasticizer may be represented by the following Formulas(16)-(20):

in which n is an integral number ranged from 3-20,000.

In some embodiments, the basic groups of the base molecules may beattracted to the acidic groups of the polymer. For example, the polymerwith the base material may be represented by the following formulas:

In some embodiments, the molding layer 120 has a glass transitiontemperature that is greater than or equal to a glass transitiontemperature of the patterned photoresist layer 110. According to someexamples, the glass transition temperature of the molding layer 120 is10-100° C. higher than that of the patterned photoresist layer 110,specifically 15-70° C. higher than that of the patterned photoresistlayer 110, more specifically 20-60° C. higher than that of the patternedphotoresist layer 110. For instance, the glass transition temperature ofthe molding layer 120 may be managed by the selections of the polymer,the base material, and/or the plasticizer. In examples, the glasstransition temperature of poly(4-styrenesulfonic acid) is about 106° C.While poly(4-styrenesulfonic acid) is mixed with a suitable amount ofammonium hydroxide, the glass transition temperature thereof may beincreased to about 136° C. In addition, when the molding layer 120includes the base material and the polymer, the base material increasesthe solubility of the molding layer 120 in several solvents such aswater, alcohol, etc. The increase in the solubility of the molding layer120 is beneficial to the subsequent process. In some embodiments, themolar ratio of the polymer to the base material ranges from 0.01 to 1.3,specifically from 0.05 to 1.0, more specifically from 0.1 to 0.6.According to some examples, when the range of the molar ratio of thepolymer to the base material is within the aforementioned range, themolding layer 120 may work an excellent “molding” for the patternedphotoresist layer 110 in subsequent operation S13 and may providesufficient solubility for the subsequent operation S14. According tosome examples, when the glass transition temperature of the moldinglayer 120 is too high, such as for example 100° C. higher than that ofthe patterned photoresist layer 110, the difficulty of the removable ofthe molding layer 120 in subsequent process may be increased.

In yet some embodiments, however, the glass transition temperature ofthe molding layer 120 may be less than that of the patterned photoresistlayer 110, which will be described in detail hereinafter in connectionwith FIGS. 8 and 9.

Referring back to FIG. 1, the method 10 proceeds to operation S13 byreflowing the patterned photoresist in the molding layer. FIG. 6 is across-sectional view schematically showing the structure after theoperation S13 is carried out, according to some embodiments of thepresent disclosure. The operation S13, for example, may include a stepof heating the patterned photoresist layer 110 to reflow the patternedphotoresist in the molding layer. In some examples, the patternedphotoresist layer 110 is heated at a temperature of greater than a glasstransition temperature of the patterned photoresist layer 110, but lessthan the glass transition temperature of the molding layer 120. Inparticular, because the patterned photoresist layer 110 is subjected tothe temperature of higher than the glass transition temperature, thepatterned photoresist layer 110 is soften, and the rough edge of thepatterned photoresist layer 110 becomes gentler or flatter due to thetendency toward the lowest free energy. Accordingly, the roughness onthe sidewall of the patterned photoresist layer 110 is reduced, and theLER issue may be improved or even remedied. On the other hand, becausethe glass transition temperature of the molding layer 120 is higher thanthe heating temperature, the molding layer 120 serves as a hard mold tosecure the basic shape (e.g., the top width, bottom width, and/or aspectratio) of the patterned photoresist layer 110. Consequently, thereflowed patterned photoresist layer 110 with less edge roughness maystill function well in the subsequent processes such as etchingprocesses. It is noted that the tiny space 114 (shown in FIG. 5) betweenthe molding layer 120 and the patterned photoresist layer 110 allows thepatterned photoresist layer 110 to be microscopically reshaped by thereflowing, even though the molding layer 120 serves as a hard mold.

The method 10 proceeds to operation S14 by removing the molding layer120 from the reflowed patterned photoresist layer 110, as shown in FIG.7. In some embodiments, the removal of the molding layer 120 includesapplying a solvent to dissolve the molding layer 120, whereas thereflowed patterned photoresist layer 110 is not dissolved. As mentionedabove, in the embodiments where the molding layer 120 includes the basematerial, the base material increases the solubility of the moldinglayer 120 in water, and therefore the molding layer 120 may be dissolvedby water in a short time period. In examples, the molding layer 120includes poly(4-styrenesulfonic acid) and a suitable amount of ammoniumhydroxide, and the molding layer 120 may be dissolved in by water within15 seconds.

The reflowed patterned photoresist layer 110 with less edge roughnessmay be used in the subsequent etching processes, and the patternedphotoresist layer 110 functions well. In examples, the subsequentetching processes may be medium-density plasma etching techniques orhigh-density plasma etching techniques utilizing inductive, helicon, orelectron cyclotron resonance (ECR) plasmas, or other suitable etchingtechniques such as for example reactive ion etching (RIE) processes.

In comparative examples where the molding layer 120 is not formedcovering the patterned photoresist layer 110, the patterned photoresistlayer 110 collapses and the shape thereof can not be maintained at anacceptable level.

Reference is made to FIG. 8, which schematically shows the formedmolding layer 120 after the operation S12 is carried out, according toyet some embodiments. In these embodiments, the tiny space 114 shown inFIG. 5 may not be required. In specifics, the molding solution offorming the molding layer 120 may have a relatively lower surfacetension, and the molding solution enters into the micro cavities orrecesses on the rough sidewall of the patterned photoresist layer 110.As a result, after the molding solution is dried, the tiny space may notsubstantially present in between the molding layer 120 and the patternedphotoresist layer 110.

As mentioned above, the glass transition temperature of the moldinglayer 120 may be less than that of the patterned photoresist layer 110according to yet some embodiments of the present disclosure. Referenceis made to FIG. 9, which schematically shows the obtained structureafter the operation S13 is performed. When the patterned photoresistlayer 110 is heated at a temperature of higher than the glass transitiontemperature, both the molding layer 120 and the patterned photoresistlayer 110 are reflowed because the glass transition temperature of themolding layer 120 is less than that of the patterned photoresist layer110. However, since the molding layer 120 occupies the major space thatsurrounds the patterned photoresist layer 110, the molding layer 120serves as a “resist” to prevents the patterned photoresist layer 110from significant collapse or flow down. Therefore, the basic shape(e.g., the top width, bottom width, and/or aspect ratio) of thepatterned photoresist layer 110 may be secured. On the other hand, sincethe heating temperature is higher than the glass transition temperaturesof both of the patterned photoresist layer 110 and the molding layer120, both of the materials (i.e., the patterned photoresist layer 110and the molding layer 120) are soften, and the rough edge of thepatterned photoresist layer 110 becomes gentler or flatter.Consequently, the reflowed patterned photoresist layer 110 with lessedge roughness may still function well in the subsequent processes suchas etching processes. Accordingly, the LER issue is improved or evenremedied. In some examples, the molding layer 120 has a glass transitiontemperature that is 3-30° C. less than the glass transition temperatureof the patterned photoresist layer 110. For example, the glasstransition temperature of the molding layer 120 is 5° C., 10° C., 15°C., 20° C., or 25° C. less than the glass transition temperature of thepatterned photoresist layer 110. According to some examples, when theglass transition temperature of the molding layer 120 is too low, suchas for example 40° C. less than that of the patterned photoresist layer110, the “molding” function of the molding layer 120 is unsatisfied.

FIG. 10 is a flow chart illustrating a method 20 according to yetvarious embodiments of the present disclosure. FIGS. 11-15 schematicallydepict the cross-sectional views in various process stages of the method200. The method 20 includes an operation S21 of forming a patternedphotoresist on a substrate, in which the patterned photoresist hasunreacted acid-labile groups. The implementation of the patternedphotoresist layer 110 described hereinbefore in connection with theoperation S11 and FIGS. 2-3 may equally applied to the operation S21,according to some embodiments. Therefore, the description of theoperation S21 is omitted herein to avoid repetition. In specifics, therough edge or sidewall of the patterned photoresist layer 110 has anumber of micro protrusions and micro cavities (or recesses), asdescribed hereinbefore.

The method 20 proceeds to operation S22 by forming a polymer layercovering the patterned photoresist. In some embodiments, a polymersolution may be applied (e.g., coating) onto the substrate 100 to form alayer of polymer solution covering the patterned photoresist layer 110.Thereafter, a drying process may be carried out to remove the solvent ofthe polymer solution. Therefore, as shown in FIG. 11, a dried polymerlayer 130 is formed covering the patterned photoresist layer 110 on thesubstrate 100. In examples, the polymer solution of forming the polymerlayer 130 may have a relatively lower surface tension, and the polymersolution enters into the micro cavities or recesses on the roughsidewall of the patterned photoresist layer 110. As a result, after thepolymer solution is dried, the micro cavities (or recesses) of thepatterned photoresist layer 110 are substantially filled up and the tinyspace is not substantially present in between the polymer layer 130 andthe patterned photoresist layer 110. Therefore, the polymer layer 130 isin contact with and surrounds the patterned photoresist layer 110. Insome embodiments, the polymer layer 130 is capable of producing orgenerating protons. For example, when the polymer layer 130 is heated,the function groups of the polymer layer 130 produces or releasesprotons. Illustrative examples of the polymers capable of producing orgenerating protons include polymers having functional group of —SO₃H,and/or —SO₃R, in which R is a leaving group when being heated. Forexample, R may be —Na or —O—(CH₃)₃. In example, the polymer layer 130may include a polymer represented by the following formulas:

In some embodiments, the polymer layer 130 may includepoly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).

In some embodiments, the polymer layer 130 may a copolymer, whichincludes at least one of the repeating unit of Formulas (1), (2), (7)and (8) and another repeating unit of Formulas (3), (4), (5), and (6).

In some embodiments, the polymer of the polymer layer 130 may be ablending polymer which includes two or more polymers or copolymersdescribed above in connection with the polymer layer 130.

In some embodiments, the polymer layer 130 may further include aplasticizer. Illustrative examples of the plasticizer includesdi(2-ethylhexyl) phthalate (DEHP), diisononylcyclohexane-1,2-dicarboxylate (DINCH), succinate, maleate, and the like,and a combination thereof. The plasticizer may function to adjust theglass transition temperature of the polymer layer.

In some embodiments, the polymer layer 130 is substantially free of abase substance which neutralizes acid or protons.

The method 20 proceeds to operation S23 by heating the polymer layer toproduce protons (H⁺), and further reacting the produced protons with theunreacted acid-labile groups of the patterned photoresist. In someembodiments, the unreacted acid-labile groups are hydrophobic, and thesurface of the patterned photoresist with the unreacted acid-labilegroups is hydrophobic. As shown in FIG. 12, when the polymer layer 130is heated, the polymer layer 130 is capable of producing protons (H⁺).The produced protons (H⁺) react with the hydrophobic acid-labile groupson the surface of the patterned photoresist layer 110 such that at leastportions of the hydrophobic acid-labile groups are transformed intohydrophilic groups. Consequently, a hydrophilic portion 116 is formed onthe surface of the patterned photoresist layer 110.

Reference is made to FIG. 13, which illustrates more details regardingthe reaction of acid-labile groups (ALGs) according to some examples. Asillustrated, the polymer layer 130 are shown by the formula of:

When the polymer layer 130 is heated, the polymer layer 130 producesprotons (H⁺). The protons (H⁺) is then reacted with the hydrophobic ALGson the surface of the patterned photoresist layer 110, and therefore thehydrophobic ALGs is converted into hydrophilic groups such as —COOH, asshown FIG. 14. Consequently, the hydrophilic portion 116 is formed onthe surface of the patterned photoresist layer 110. It is noted that theinner portion 118, covered by the hydrophilic portion 116, is stillhydrophobic because the diffusion of the protons (H⁺) is controlled tobe limited to a certain distance from the surface of the patternedphotoresist layer 110. Furthermore, the protrusive portions of thepatterned photoresist layer 110 have a thicker hydrophilic region, ascompared to the cavities or recessed portions, because the protrusiveportions provide a relatively larger contact area with the polymer layer130. Accordingly, the inner hydrophobic portion 118 has a smallerroughness, as shown in FIG. 14.

According to some embodiments of the present disclosure, in theoperation S23 of heating the polymer layer 130 to produce the protons(H⁺), the patterned photoresist layer 110 may concurrently be reflowedin the polymer layer 130. In specifics, the polymer layer 130 may beheated to a temperature that is greater than the glass transitiontemperature of the patterned photoresist layer 110, and therefore thepatterned photoresist layer 110 may be reflowed concurrently.Alternatively, another heating step may be performed to reflow thepatterned photoresist layer 110 after the operation S23 is carried out.Therefore, the roughness of the sidewall of the patterned photoresistlayer 110 may be reduced during or after the operation S23. It is notedthat the glass transition temperature of the polymer layer 130 may beless than, substantially equal to, or greater than that of the patternedphotoresist layer 110. Furthermore, the polymer layer 130 may also bereferred to as a molding layer 120 in some embodiments describedhereinafter.

The method 20 proceeds to operation S24 by removing the polymer layerfrom the patterned photoresist. In some embodiments, as shown in FIG.15, the removal of the polymer layer 130 includes applying a solvent todissolve the polymer layer 130 and the hydrophilic portion 116 on thesurface of the patterned photoresist layer 110, but the inner portion118 of the patterned photoresist layer 110 is not dissolved. After thehydrophilic portion 116 of the patterned photoresist layer 110 and thepolymer layer 130 are removed, the inner portion 118 of the patternedphotoresist layer 110 is exposed. As discussed above, the inner portion118 has a smaller roughness on the sidewall, and therefore the LER issueof the patterned photoresist layer 110 is improved or even remedied.Stated differently, the removable of the polymer layer 130 may reducethe roughness on the sidewall of the patterned photoresist layer 110,according to some embodiments.

According to yet some embodiments, the method 10 of FIG. 1 and themethod 20 of FIG. 10 may be combined together. FIG. 16 is a follow chartillustrating a method 30 according to some embodiments of the presentdisclosure, which include features of method 10 and method 20.

The method 30 includes operation S31 of forming a photoresist layer 106on a substrate 100, as shown in FIG. 2. In examples, a photoresistsolution may be applied (e.g., coating) on the substrate 100, andfollowed by a drying process to remove the solvent in the photoresistsolution. Accordingly, the photoresist layer 106 is blanketly formed onthe substrate 100.

The method 30 further includes operation S32 of exposing and developingthe photoresist layer 106 to form a patterned photoresist layer 110, asshown in FIG. 3. The patterned photoresist layer 110 includeshydrophobic acid-labile groups.

The method 30 further includes operation S33 of forming a molding layer120 covering the patterned photoresist layer 110, as shown in FIG. 5, inwhich the depicted space 114 may or may not appear. According to someembodiments of the present disclosure, the molding layer 120 has a glasstransition temperature that is greater than or equal to a glasstransition temperature of the patterned photoresist layer 110. In someembodiments, however, the glass transition temperature of the moldinglayer 120 is 10° C.-30° C. less than the glass transition temperature ofthe patterned photoresist layer 110.

The method 30 further includes operation S34 of heating the moldinglayer 120 at a temperature higher than a glass transition temperaturethereof to generate protons (H⁺) from the molding layer 120. In someembodiments, the molding layer 120 is heated to the temperature that isgreater than glass transition temperatures of both the molding layer 120and the patterned photoresist layer 110. In yet some embodiments, themolding layer 120 is heated to the temperature that is greater than theglass transition temperatures of the molding layer 120, but less thanthe glass transition temperature of the patterned photoresist layer 110.

The method 30 further includes operation S35 of reacting the generatedprotons from the molding layer 120 with the hydrophobic acid-labilegroups of the patterned photoresist layer 110, as shown in FIGS. 12-14.The operation S35 further includes transforming a portion of thehydrophobic acid-labile groups into hydrophilic groups, and therefore ahydrophilic portion 116 is formed on a surface of the patternedphotoresist layer 110. The embodiments of operation S23 in the method 20may be equally applied to the operation S35 described herein, andtherefore the details of the operation S35 are not repeated herein.

The method 30 further includes operation S36 of, as shown in FIG. 15,removing the molding layer 120 and the hydrophilic portion 116 on thesurface of the patterned photoresist layer 110 to reduce a surfaceroughness of the patterned photoresist layer 110. According to someembodiments of the present disclosure, the removable of the moldinglayer 120 and the hydrophilic portion on the surface of the patternedphotoresist includes applying a solvent to dissolve the molding layer120 and the hydrophilic portion 116 on the surface of the patternedphotoresist layer 110.

In accordance with one aspect of some embodiments, a method of forming apatterned masking layer (e.g., photoresist) includes the followingoperations: (i) forming a patterned photoresist on a substrate; (ii)forming a molding layer covering the patterned photoresist; (iii)reflowing the patterned photoresist in the molding layer; and (iv)removing the molding layer from the reflowed patterned photoresist.

In some embodiments, the operation of reflowing the patternedphotoresist includes heating the patterned photoresist at a temperatureof greater than a glass transition temperature of the patternedphotoresist.

In some embodiments, the molding layer has a glass transitiontemperature that is greater than or equal to the glass transitiontemperature of the patterned photoresist.

In some embodiments, the molding layer has a glass transitiontemperature that is 3° C.-30° C. less than the glass transitiontemperature of the patterned photoresist.

In some embodiments, the operation of reflowing the patternedphotoresist includes reducing a roughness on a sidewall of the patternedphotoresist.

In some embodiments, the molding layer includes a polymer having arepeating unit including at least one of a hydroxyl functionality, acarboxylate functionality, a carboxylic acid functionality, an aminefunctionality, and an amide functionality.

In some embodiments, the molding layer further includes a base materialdispersed in the polymer, and the base material includes ammoniumhydroxide, (2-Methylbutyl)amine, (3-Methylpentyl)amine,2,4,6-Trimethylpyridin-3-amine, or 5-methylpyrimidin-2-amine, or acombination thereof.

In some embodiments, the molding layer further includes a plasticizerselected from the group consisting of di(2-ethylhexyl) phthalate (DEHP),diisononyl cyclohexane-1,2-dicarboxylate (DINCH), succinate, andmaleate.

In some embodiments, the patterned photoresist includes a plurality ofapertures exposing the substrate, and the operation of forming themolding layer covering the patterned photoresist includes filling up theapertures with the molding layer.

In some embodiments, the operation of reflowing the patternedphotoresist in the molding layer includes heating the patternedphotoresist and producing protons from the molding layer.

In accordance with one aspect of some embodiments, a method of reshapinga patterned photoresist includes the following operations: (i) forming apatterned photoresist on a substrate, wherein the patterned photoresisthas unreacted acid-labile groups; (ii) forming a polymer layer coveringthe patterned photoresist; (iii) heating the polymer layer to produceprotons, and reacting the produced protons with the unreactedacid-labile groups of the patterned photoresist; and (iv) removing theheated polymer layer from the patterned photoresist after the heatingthe polymer layer to produce the protons.

In some embodiments, the method further includes reflowing the patternedphotoresist in the polymer layer after or during the operation ofheating the polymer layer but prior to the operation of removing thepolymer layer from the heated polymer layer.

In some embodiments, the operation of reflowing the patternedphotoresist in the polymer layer includes reducing a roughness on asidewall of the patterned photoresist.

In some embodiments, the unreacted acid-labile groups are hydrophobic,and the reacting the produced protons with the unreacted acid-labilegroups of the patterned photoresist includes transforming a portion ofthe unreacted acid-labile groups into hydrophilic groups, therebyforming a hydrophilic portion on a surface of the patterned photoresist.

In some embodiments, the operation of removing the heated polymer layerfrom the patterned photoresist includes reducing a roughness on asidewall of the patterned photoresist.

In some embodiments, the operation of removing the heated polymer layerfrom the patterned photoresist includes applying a solvent to dissolvethe heated polymer layer and the hydrophilic portion on the surface ofthe patterned photoresist.

In accordance with one aspect of some embodiments, a method of forming apatterned photoresist includes the following operations: (i) forming aphotoresist layer on a substrate; (ii) exposing and developing thephotoresist layer to form a patterned photoresist layer includinghydrophobic acid-labile groups; (iii) forming a molding layer coveringthe patterned photoresist layer; (iv) heating the molding layer at atemperature higher than a glass transition temperature thereof toproduce protons from the molding layer; (v) reacting the producedprotons from the molding layer with the hydrophobic acid-labile groupsof the patterned photoresist layer to transform a portion of thehydrophobic acid-labile groups into hydrophilic groups, thereby forminga hydrophilic portion on a surface of the patterned photoresist layer;and (vi) removing the molding layer and the hydrophilic portion on thesurface of the patterned photoresist layer to reduce a surface roughnessof the patterned photoresist layer.

In some embodiments, the molding layer has a glass transitiontemperature that is greater than or equal to a glass transitiontemperature of the patterned photoresist layer.

In some embodiments, the molding layer has a glass transitiontemperature that is 10° C.-30° C. less than a glass transitiontemperature of the patterned photoresist layer.

In some embodiments, the removing the molding layer and the hydrophilicportion on the surface of the patterned photoresist layer includesapplying a solvent to dissolve the molding layer and the hydrophilicportion on the surface of the patterned photoresist layer.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: forming a patternedphotoresist on a substrate; forming a molding layer covering thepatterned photoresist; reflowing the patterned photoresist in themolding layer; and removing the molding layer from the reflowedpatterned photoresist.
 2. The method according to claim 1, wherein thereflowing the patterned photoresist comprises heating the patternedphotoresist at a temperature of greater than a glass transitiontemperature of the patterned photoresist.
 3. The method according toclaim 2, wherein the molding layer has a glass transition temperaturethat is greater than or equal to the glass transition temperature of thepatterned photoresist.
 4. The method according to claim 2, wherein themolding layer has a glass transition temperature that is 3° C.-30° C.less than the glass transition temperature of the patterned photoresist.5. The method according to claim 1, wherein the reflowing the patternedphotoresist comprises reducing a roughness on a sidewall of thepatterned photoresist.
 6. The method according to claim 1, wherein themolding layer comprises a polymer having a repeating unit comprising atleast one of a hydroxyl functionality, a carboxylate functionality, acarboxylic acid functionality, an amine functionality, and an amidefunctionality.
 7. The method according to claim 6, wherein the moldinglayer further comprises a base material dispersed in the polymer, andthe base material comprises ammonium hydroxide, (2-Methylbutyl)amine,(3-Methylpentyl)amine, 2,4,6-Trimethylpyridin-3-amine, or5-methylpyrimidin-2-amine, or a combination thereof.
 8. The methodaccording to claim 6, wherein the molding layer further comprises aplasticizer selected from the group consisting of di(2-ethylhexyl)phthalate (DEHP), diisononyl cyclohexane-1,2-dicarboxylate (DINCH),succinate, and maleate.
 9. The method according to claim 1, wherein thepatterned photoresist comprises a plurality of apertures exposing thesubstrate, and the forming the molding layer covering the patternedphotoresist comprises filling up the apertures with the molding layer.10. The method according to claim 1, wherein the reflowing the patternedphotoresist in the molding layer comprises heating the patternedphotoresist and producing protons from the molding layer.
 11. A method,comprising: forming a patterned photoresist on a substrate, wherein thepatterned photoresist has unreacted acid-labile groups; forming apolymer layer covering the patterned photoresist; heating the polymerlayer to produce protons, and reacting the produced protons with theunreacted acid-labile groups of the patterned photoresist; and removingthe heated polymer layer from the patterned photoresist after theheating the polymer layer to produce the protons.
 12. The methodaccording to claim 11, further comprising reflowing the patternedphotoresist in the polymer layer after or during heating the polymerlayer but prior to the removing the polymer layer from the heatedpolymer layer.
 13. The method according to claim 12, wherein thereflowing the patterned photoresist in the polymer layer comprisesreducing a roughness on a sidewall of the patterned photoresist.
 14. Themethod according to claim 11, wherein the unreacted acid-labile groupsare hydrophobic, and the reacting the produced protons with theunreacted acid-labile groups of the patterned photoresist comprisestransforming a portion of the unreacted acid-labile groups intohydrophilic groups, thereby forming a hydrophilic portion on a surfaceof the patterned photoresist.
 15. The method according to claim 14,wherein the removing the heated polymer layer from the patternedphotoresist comprises reducing a roughness on a sidewall of thepatterned photoresist.
 16. The method according to claim 14, wherein theremoving the heated polymer layer from the patterned photoresistcomprises applying a solvent to dissolve the heated polymer layer andthe hydrophilic portion on the surface of the patterned photoresist. 17.A method, comprising: forming a photoresist layer on a substrate;exposing and developing the photoresist layer to form a patternedphotoresist layer including hydrophobic acid-labile groups; forming amolding layer covering the patterned photoresist layer; heating themolding layer at a temperature higher than a glass transitiontemperature thereof to produce protons from the molding layer; reactingthe produced protons from the molding layer with the hydrophobicacid-labile groups of the patterned photoresist layer to transform aportion of the hydrophobic acid-labile groups into hydrophilic groups,thereby forming a hydrophilic portion on a surface of the patternedphotoresist layer; and removing the molding layer and the hydrophilicportion on the surface of the patterned photoresist layer to reduce asurface roughness of the patterned photoresist layer.
 18. The methodaccording to claim 17, wherein the molding layer has a glass transitiontemperature that is greater than or equal to a glass transitiontemperature of the patterned photoresist layer.
 19. The method accordingto claim 17, wherein the molding layer has a glass transitiontemperature that is 10° C.-30° C. less than a glass transitiontemperature of the patterned photoresist layer.
 20. The method accordingto claim 17, wherein the removing the molding layer and the hydrophilicportion on the surface of the patterned photoresist layer comprisesapplying a solvent to dissolve the molding layer and the hydrophilicportion on the surface of the patterned photoresist layer.